Holography is concerned with techniques for producing images, especially three dimensional images, by reconstructing wave fronts of light. In most holographic techniques, lasers are utilized to record a diffraction pattern on a photographic plate. This diffraction pattern is subsequently utilized to generate a three dimensional image. FIGS. 1a and 1b illustrate in more detail the recording of the diffraction pattern and the subsequent generation of a holographic image from the diffraction pattern, as typically performed in holographic techniques. In generating the diffraction pattern two beams of laser light are used: a reference beam 4 and an object beam 3. In most instances, both the object beam 3 and the reference beam 4 originate from a single laser source. The object beam 3 is directed to strike an object (FIG. 1a). Light from the object beam reflects off the object 1 and strikes the photographic plate 2 together with the reference beam 4. Because of the mutual degree of coherence between the object beam 3 and the reference beam 4, an interference pattern occurs on the plate 2 which is recorded by the photographic plate 2.
Once the interference pattern has been recorded on the photographic plate 2, the plate 2 is developed using traditional photographic techniques. Subsequent to development of the photographic plate, a holographic image may be generated by shining a reconstruction beam 8 (i.e. the reference beam 4) through the plate 2 as shown in FIG. 1b. As the reconstruction beam 8 passes through the holographic plate 2, it is diffracted by the recorded interference pattern now described as a generalized diffraction grating and generates a virtual image 9 of the object that is visible to a viewer 7. Thus, the viewer 7 is given the illusion of actually seeing the object.
The above description represents just one of the many techniques for generating holographic images. The basic concepts elaborated with respect to that technique, however, are equally applicable to other approaches of generating such images.
Attempts at real time three dimensional holographic display systems have been plagued with bandwidth and display technology problems. In particular, the necessary bandwidth of information required to produce holographic images has been too great for current processing capabilities. For instance, a hologram of dimensions 100 millimeters by 100 millimeters and a viewing angle of 30 degrees contains approximately 25 gigabytes of information. This is the equivalent of 25 billion samples of information. Moreover, in order to update such an image with 8 bit resolution at rate of 60 frames per second, a data rate of 12 terabits/seconds is required for transmission of the hologram. These tremendous bandwidth and processing requirements are far beyond current capabilities.